1. Field of the Invention
The present invention relates to a seatbelt reminder system, and, more particularly, to a seatbelt reminder system which optimizes the start of giving a warning.
2. Description of the Related Art
In general, seatbelts in a vehicle are capable of fastening the bodies of crew members to their seats. Accordingly, a seatbelt reminder system is used to avoid the unfastened state of each seatbelt as much as possible.
The system employs different reminder schemes, such as a visual warning to visually notify the unfastened state of the seatbelt to a crew member by means of, for example, lighting of an indicator, and an acoustic warning to give acoustic notification to the crew member by giving a buzzer sound.
With regard to visual warning, for example, the seatbelt reminder system has various reminder schemes, such as giving a reminder by lighting an indicator until a seatbelt is fastened, and giving a first reminder by lighting an indicator for about 60 seconds and giving a second reminder by repeating flickering, achieved by light-ON for several seconds and light-OFF for several seconds, several times following the first reminder. There has been proposed a technique of allowing the system to clearly define the first reminder and the second reminder and give the defined reminders (U.S. Pat. No. 6,278,358).
The system gives the first reminder when the ignition key is switched ON from the OFF state, and gives the second reminder when a seatbelt is in an unfastened state even after the first reminder has been given.
To urge a crew member to fasten a seatbelt, the prior art technique clearly defines the first reminder to urge prompt fastening of a seatbelt and the second reminder to further urge the prompt fastening. In the case where the start condition for the second reminder is satisfied when the first reminder is finished, however, the second reminder is executed following the first reminder. That is, the first reminder and the second reminder are given consecutively, making it hard for a crew member to recognize the second reminder, so that fastening of the seatbelt cannot be urged properly.
In the system that uses visual warning and acoustic warning in parallel, particularly, when the condition for the second reminder is satisfied while the indicator is lit for about 60 seconds for visual warning with a seatbelt unfastened, buzzing as acoustic warning starts while the second reminder takes place with the indicator kept lit for visual warning. In some case, therefore, this makes a crew member notice the initiation of only the acoustic warning and makes it hard for the crew member to understand the meaning of this reminder. Even if the first reminder and the second reminder are clearly defined, therefore, there still remains an issue of how to make a crew member notice the reminders.